Jacoby
method of well completion



Nov. 10, 1964 c. H. JAcoBY METHOD OF WELL COMPLETION 2 Sheets-Sheet 1Original Filed April 20, Y1959 INVENTOR.' CHARLES H. JAcosy TTOENE' YSC. H. JACOBY METHOD 0F WELL COMPLETION y f E 2 R .w M@ m M 8 Y N u T...l IH. R e L L O E s n k2 L U, L m o m l A s H A ...1... 4 nu @w E?. a. 3O .....,...f. C i -l.|-

Nov. 10, 1964 Original Filed April 2 0, 1959 x EMjNZj .j

SPL/TTING OR FRAcrus/NGAREA Reissue-d Nov. 19, 19t

25,682 METHD OF WELL CGMPLETIQN Charles H. Jacoby, Dearborn, Mich.,assigner to The International Salt Company, Inc., Scranton, Pa.

Original No. 3,064,957, dated Nov. 20, 1962,'Ser. No.

807,449, Apr. 20, 1959. Application for reissue Jan.

22, 1964, Ser. No. 350,929

7 Claims. (Cl. 299-4) Matter enclosed in heavy brackets appears in theoriginal patent but forms no part of this reissue speeldcation; matterprinted in italics indicates the additions made by reissue. 1

This invention relates to the mining of l1qu1d-solubre minerals fromunderground strata, and more particularly to the solution mining ofsalt. It is well known that soluble mineral deposits may be recovered bythe drilling of wells into the mineral strata, fracturing the strata toopen a passageway from one well to another and then circulating amineral solvent through the opened underground system. Such a system ofinterconnected wells and cavities is referred to as a gallery. It isalso well known in the art that the solution mining of salt hasparticular difficulties due primarily to the fact that when water ispumped into a well drilled into a salt formation the Jfresh water willtend to rise and the brine-saturated Water remains near the bottom ofthe cavity. As a result the formed cavity develops primarily upwardlyand only secondarily laterally. This condition isY further developed byreason of the insoluble impurities in the salt deposit falling out ofthe brine solution and forming a semiporous insoluble blanket on theiloor and to some degree, the walls of the cavity. It is of courseobvious that in order to obtain any worthwhile amount of salt underthese circumstances it is necessary to drill the well to the bottom ofthe salt strata and even then a great deal of the deposit will bewasted` Because of the aforesaid conditions it was a natural developmentto utilize the gallery system for solution mining of salt, and this isdiscussed in a number of letters patents, examples of which are Patents1,960,932 to Tracy, 2,487,202 to Pullen and 2,850,270 to Hanson.

It is a primary object of the present invention to provide an improvedmethod for completing a well driven into and through an undergroundstrata of mineral to be recovered by the dissolution mining process.

A specific object of the present invention is to provide an improvedmethod of sealing oil a well that has been driven through a salt bed andinto the strata therebelow so that the subsequent fracturing orsplitting operation will be limited to within the salt bed while stillbeing coniined to the lower level thereof.

Another object is to provide an improved method for sealing the well inrelation to the strata above and below the bed to be mined, by means ofan improved concrete sheath and seal.

Still another object of the invention is to so locate and completedrilled wells which are to be interconnected so as to secure improvedresults 4in the mining oper-ation by more efficient use of the liquidsolvent circulated through the gallery system.

Other objects and advantages of the invention will appear inthespecification hereinafter and in the drawings wherein:

FIG. l is a diagrammatic vertical sectional view taken through strataincluding a salt bed to be mined by circulation of water/through aninjection well and fractured strata to the production well;

FIG. 2 .is a fragmentary sectional view, on enlarged scale, taken asindicated at Il-II of FIG. l, showing the lower portion of the completedwell in more detail.

Referring now to FIG. 1, a target well 12, and injection well 14 have'been drilled into a salt strata and an und ground connection has beeneffected as by splitting a uplifting the salt bed as indicated at 15,thereby establi ing a gallery for the purpose of solution mining throt`interconnected well In accordance with my improi method, the Iinjectionwell 14 is drilled and completed follows:

I prefer to use a rotary drill for sinking the hole cause I believe itallows a better bond between the vv rock and the cement shea'di which isprovided around well casing, as will be described hereinbelow, by lessenthe possible number of air-and water entrapment vo created by a roughwall and eliminates a major port of the detrital Slough which is createdby running cas in a rough-walled hole. Such Slough rock will tend followthe casing down the hole and will often fo partial or total blockages inthe aunulus between the h wall and casing. Usually a l2 to l5 diameterholt desirable and the hole 14 will be started with the propriate rotarybit. As it is desirable to have accur knowledge of the location of thebottom of the salt str and the composition of both the salt strata andthe jacent roclc formation, when a point approximately feet above thecalculated top of salt is reached, may use a 6l/zl core bit to corethrough -all the ma salt stratum and into enough of the underlying strto determine its exact nature. Alternatively, it would less accurate butalso less expensive if the normal h were continued and logged by somegeophysical me such as gamma ray logging.

I have found that improved cavity and gallery fori tion is obtained byconfining the well-interconnect split to the salt strata. This isbecause the roel: fori tions underlying sait deposits, although notnecessa' soluble, are in general, much more permeable horizon ly thanthe salt. An uplift in these planes would al considerable and possiblytotal loss of injection ll. Accordingly, when the above mentioned coringis inisl the hole is drilled on down approximately three i into the rockunderlying the salt and the hole is t plugged back, preferably with asuitable expand cement 24, to a point about two feet above bottom salt,as indicated at 25. This will effectively seal od hole from theunderlying rock. The casing 26 is t run into the hole and set to withinabout two feet the top of the plug as shown in FIG. 2. The dimensi givenare respesentative only. The specific measl ments will depend upon theactual rock and salt cor tions found at each particular well site. Iselect a zi within the lower portion of the salt strata which is pureand as free of insolubles as possible. The lo tensile strength of thepure salt and the greater solubi thereof will aid in the splitting ofthe bed and subsequ wash-through operations. In any case the gap betwthe end of the casing and the plug in the hole bottom be kept as smallas practicable because this will be point of application of thesplitting fluid pressure. point of application of the splitting anduplifting press is confined to as small a vertical portion of the holspossible because this reduces the possibility of caus multiplehorizontal fractures within the same salt bed. two or more independentpartings occur, the volume iiuid required to complete a fracture to thepoint of in section with the target well will be greatly increased,proper development of the cavity during mining may impaired. Given asmall wall area exposed to spliti pressure, salt deposits may behorizontally split and lifted much more satisfactorily than most rockfori tions because of the low tensile strength of the salt because itsbed planes generally run evenly horizonta After the core hole l and mainhole 14 have b plugged back and the casing set, the next step isv`tblish a cement sheath around the outside or" the ing to ill theannular space between the casing and hole wall. The cement sheath servesto reinforce casing, insulate the casing against corrosive inlluences l1as ground waters which in many locations often .tain considerableamounts of hydrogen sulphide and monia together with other corrosivesalts, and to seal the hole above the lower end of the casing againstsible vertical tracturing when the splitting pressur ntroduced, andagainst vertical escape of injection :l alongside the casing duringwash-through operations. n order to obtain the best possible sealingeffect it lesirable to have the cement sheath devoid of any :ks orfissures and to have the sheath bonded to the 'ounding rock. l havefound the following improved hod of cementing the well to provide anexcellent ihed sheath. The cement is placed by pumping it t the casingand the cement reaching the bottom or well will be forced upwardlyaround the outside ot casing. Since the material iirst pumped into theng will be that which ultimately fills the space been the casing and'the wall rock around the upper or of the well as indicated at 28, therst cement ined into the casing is preferably regular Portland .entmixed with fresh water. The fresh water cement allowed by batch ofbrine-based cement which Will .fide an improved sheathing of the lowerend of the ng in the salt strata as indicated at .'50, because water- :dcemento will not bond with salts whereas the e based cement will bondwith the beds of salt and ydrite. Fine granulated salt is mixed with thebrinerd cement in proper amounts depending on roel; peratures, thetemperature of the brine at the mixing lt and the ground waterconditions immediately above salt sections, to maintain the brine in thesaturated At the linal stage of cementing, 2% by weight :alcium chlorideis added to the cement which will .th the lower-most end of the casingas indicated at So as to cause this portion of the cement to setupharden before the major portion of the cement above As soon as thecalcium chloride containing portion 1e cement sheath has set the cementin and under the of the casing is drilled out down to the expanded entplug 24 i the hole bottom and an expansion 1er is used to remove therest of the concrete from 1nd the hole wall, from the bottom point ofthe 1g to the top of the plug, thus leaving the salt Wall ased over thisarea as indicated at 34. This is the t to be subjected to splittingpressure.

lternatively, before cementing, water, gravel or other arial may beplaced in the hole bottom to form a pad iacer. This pad will keep thecement from filling the 'e gap between the casing and the bottom plugand, 1 removed after cementing is completed, will leave lesired area ofthe salt wall exposed. f course any vn method may be used to exposedesired areas of ialt deposit to the splitting media by perforating theent sheath or the sheath and casing.

ie use of the quick setting cement mixture at the lower ,on of the Wellprovides two important advantages. I, by permitting the cement at thebottom of the casing z drilled out as described, while the rest of thecement f th is still plastic or semi-liquid, the sheath is not :ct tovibration cracks which often result when the th has hardened before thedrilling-in takes place. is prevented by the hardened lower portion of:nt backing up the still plastic sheath. Secondly, a iderable amount ofwaiting time, and the attendant ng and personnel cost, is saved. :laim:

The method of completing a well driven through nirden into a saltdeposit overlying a non-salt desaid method comprising backplugging thewell with nding cement to the elevation of the bottom of the area to besubsequently split, running a casing into the well to the top of saidarea, pumping water-based cement into said casing in a quantity suicientto lill the space between the casing and said overburden, then pumpinginto said casing a supply of brine-based cement sufficient to lill thespace between the casing and the upper portion of the salt deposit abovesaid area, then pumping into said casing a supply of calcium chloridecontaining cement suicient to till the remainder of the space betweenthe casing and the salt deposit, and then after said calcium chloridecontaining cement is set and before the balance of said cement is setroaming out the cement at the splitting arca to expose the salt stratathercat.

2. The method of completing a well driven through overburden into a saltdeposit and an underlying non-salt deposit, said method comprisingbackplugging the Well with expanding cement to the elevation of thebottom of the salt section to be fractured, running a casing into thewell to the top of said section, pumping unset cement into said casingin a quantity sufficient to ll the space between thc casing and saidoverburden, then pumping into said casing a supply of brine-based cementsuliicient to lill the space between the casing and the upper portion ofthe salt deposit above said section, then pumping into said casing asupply of calcium chloride containing brinebased cement sutlicient to llthe remainder of the space between the casing and the salt deposit, andthen reaming out the cement at the area to be split to expose the saltstrata thereat.

3. ln a method ot completing a Well driven through overburden into asalt deposit for solution mining thereof, the steps o1 baci/plugging thewell with expanding cement to the elevation of the bottom ol a salt areato be fractured, running a casing into the well to the top of said area,pumping unset cement into said casing in a quantity suilicient to lillthe space between the casing and said overburden and the upper portionof said salt deposit, then pumping into said casing a supply of cementcontaining calcium chloride suilicient to fill the remainder of thespace between the casing and the salt deposit, and then after saidcalcium chloride containing cement is set and before the balance of saidcement is set rearning out the cement at the area to be fractured toexpose the salt strata thereat.

4. {The method of mining a subterranean soluble salt deposit lying abovea non-salt strata, which method includes driving a well through saidsoluble salt deposit and into the strata therebelow, plugging back thewell to a point above the elevation of said non-salt strata and within arelatively pure salt layer, inserting a casing into said well which isof smaller diameter than the well and to a point just above the plug atthe well bottom, forcibly introducing a quantity of cement through saidcasing suliicient to fill the annular space around the casing upwardlyfrom said plug, in which the cement last introduced is quicker settingthan the previously introduced cement, cutting away the quick settingcement immediately above said plug to expose a, small vertical portionof the salt deposit when the quick setting cement has hardened and whilethe cement thereabove is still in plastic condition, and then applying asplitting and uplifting pressure Within said casing after all of thecement has hardened, preparatory to introduction of a salt solvent lluidinto the split area] 5. The method of mining a subterranean soluble[salt] mineral deposit, which method includes (a) driving a well throughsaid soluble [salt] mineral deposit and into the strata therebelow,

(b) sealing the bottom of the well by plugging back the Well to a levelwithin the region of the soluble [salt] mineral deposit,

(c) inserting a casing into said well which is of smaller diameter thanthe well and to a point just above the plug in the well bottom, (d)sealing between the casing and well by forcibly introducing cementthrough said casing to seal between the casing and well upwardly fromsaid plug,

(e) cutting away the cement to expose a small vertical portion of saidsoluble lsalt] mineral deposit in an area thereof between said plug andthe bottom of the casing after the plug and at least a lowermost portionof the cement around the casing has hardened and without disturbing thestated seals at areas either above or below the exposed portion,

(f) then applying a splitting and uplifting pressure to said [salt]soluble mineral deposit at said exposed portion thereof so that suchforce is confined solely at the exposed region, preparatory tointroduction of a [salt] soluble mineral solvent iluid into the splitarea.

6. The method according to claim 5 wherein the in- Itroduction of cementis controlled so that (a) the cement last introduced is quicker settingthan the previously introduced cement so that the quick setting cementis disposed Within the region of and extends upwardly from the plug,

(b) said [salt] soluble mineral deposit being exposed after the quicksetting cement has hardened but while the cement thereabove is still inplastic condition,

(c) the splitting and uplifting force being applied after all the cementhas hardened.

7. The method of solution mining salt] soluble mneral which includes thesteps of (a) driving a well through a soluble {salt} mineral deposit andinto underlying strata,

(b) sealing the well by introducing cement into said well to form (a) asolid plug upwardly from tht well bottom to a point Within said solublesalt] mineral deposit and (b) a casing-embracing shel above said plugand extending upwardly through a least a substantial extent of the[salt] soluble min eral deposit,

(c) cutting away the cement to expose a small vertica area of the [salt]soluble mineral deposit just abov the plug after the plug and at least alower-most por tion of said shell has hardened and without disturb ingthe seal in areas either above or below the posed portion, whereby theplug and shell are dis continuous only at said exposed portion,

(d) and thereafter applying a splitting and upliftin force within thewell so as to be confined in its a; plication solely to the exposedportion of the [salt` soluble mineral deposit to the exclusion of regionabove and below said portions.

References Cited by the Examiner The following references, cited by theExaminer, are c record in the patented tile oi this patent or theorigin:

patent.

UNITED STATES PATENTS 1,960,932 5/34 Tracy. 2,847,202 8/58 Pullen.2,850,270 9/58 Hanson. 2,952,449 9/60 Bays. 2,961,644 ll/ Shell.

BENAMN HERSH, Primary Examiner.

